The glaucoma family of intermediates consist of IOP check and variations on an IOP check. The gonioscopy is essentially an IOP check where a gonioscopy is also performed (along with dilation if the results of the gonioscopy permit it). The pachemetry is an IOP check where pachemetry is performed. The Doctor Thresh is an IOP check where Threshold and OCT testing are performed. The standard IOP check is in a 15 min slot, however, gonioscopies and doctor thresholds are in 30 min slots due to the extra time required for the testing. We will first go over the IOP check and then discuss gonioscopy and pachemetry (Thresholds and OCTs will be reserved for the Threshold module).

First, lets review what Glaucoma is.

IOP Check

CONCEPT

Patient’s who are being watched for glaucoma risk factors will, quite commonly, be brought back to have their IOP retested. These appointments are called IOP checks. Depending on the number of glaucoma risk factors a patient has, they may have multiple IOP checks before their next annual exam. This is because if the IOP spikes and remains high long enough it can damage the optic never and lead to irreversible vision loss. The doctor, at each appointment, will evaluate the patient’s risk factors and determine a reasonably safe amount of time before the IOP needs to be rechecked.

Glaucoma risk factors include: angle size, C/D ration, optic nerve thickness, visual field defects, IOP history, corneal thickness, family history, major loss of blood, sleep apnea. If the patient only has one of these risk factors, the doctor may be ok to let them go until their next annual exam before their IOP is rechecked. If a patient has multiple, the doctor may want to see them several times before their next annual exam.

During the IOP check, the doctor will retest IOPs with the tonometer, recheck the front and back of the eyes (without dilation), and perform any other testing needed at the time (such as gonioscopy, pachemetry, OCT-RFNL, OCT-Mac (GCC), Threshold).

WORKUP ORDER

Complete visual acuity, expedited medical history, if the patient is on IOP lowering drops Inquire how they are taking the drops (to make sure it matches with what was recorded in their chart) as well as how consistently they are taking the drops.

CHARTING CHECKLIST

  • Layout: Intermediate

  • Hx/Meds: Forward and update as needed.

  • Workup: Enter the patient’s glaucoma diagnosis as the chief complaint (i.e. POAG-B, NAG-B, POAG, NAG, Ocular Hypertension, etc). Fill in VAs, pupils, and EOMs. Enter IOPs when completed by the doctor.

  • Exam: Forward anterior and posterior findings and update based on the doctors findings. Forward the patient’s Glaucoma diagnosis in the plan and make it the #1 diagnosis for the appointment. Update plan to reflect all recommendations from that appointment.

  • Testing: Create entry for any testing done (gonioscopy, pachemetry, OCT)

  • Routing: Ask the doctor which office code they would like for the visit. Be sure to check the box for any testing done at that visit (gonioscopy, pachemetry, OCT, Visual Field, etc). Indicate in the additional notes box when the patient’s next appointment should be scheduled.

Pachemetry

Pachemetry is a measurement of a patient’s corneal thickness which is usually performed with a pachemeter (can also be done on some of the OCTs) by the doctor. Corneal thickness matters in relationship to glaucoma because if a patient has thick corneas their IOP readings may be artificially high. Likewise, if a patient has thin corneas, their IOP may be artificially low.

The pachemetry readings are recorded on the workup tab as seen below.

and there should also be an entry in the testing table for pachemetry.

Gonioscopy

A gonioscopy is a test that is usually done for NAG-B or NAG patients to check if the drainage angle for their aqueous humor is open enough to safely dilate. When the doctor checks angle at the exam, they are not able to look at it directly but get a gross measurement of the angle using something call the Van Herick technique which involves casting a beam of light at the cornea and comparing the size of the beam on the cornea to the size of the shadow it casts before the beam appears again on the iris. The doctor then grades the angle anywhere from 0-4 (0 being closed, 4 being wide open).


The reason why the grade of the angle matters is because when the iris dilates to allow a better view of the retina, it narrows the drainage angle. If the angle undilated is graded at 2 or less, there is potential that a dilated iris could block off the already narrow angle leading to a rapid spike in IOP and potential damage to the optic nerve. Rather than guess whether or not the angle is open enough to dilate safely based on the Van Herick measurement, the doctor will usually invite the patient to return for a test called gonioscopy where the doctor uses a special lens with mirrors that allows them to observe the drainage angle directly and determine whether or not it is safe to dilate the patient.

Please watch the following video on gonioscopy.

Some doctors prefer to record the findings themselves. Others will have you record them as follows. First create a gonioscopy entry in the testing table

The actual findings are recorded below the testing table. Use the “PIG” and “AC” dropdowns to enter the doctors findings in all four quadrants of each eye.

The AC dropdown

PIG dropdown

The doctor uses certain depth landmarks when observing the angle to notate how open it is. Here is what they might be able to observe on an open angle

verses a narrow angle.

Notice how in the open angle example, the doctor is able to observe all the way down to the Ciliary body. Whereas in the narrow angle example, the doctor is only able to observe down to the pigmented trabecular meshwork.

The abbreviations of the landmarks are as follows:

SL: Schwalbe’s Line

TM: trabecular meshwork (can be anterior, 1/2, trace, ant/tm)

SS: Scleral Spur

CB: CIliary Body

They also notate how much pigment they observe in each quadrant because, just like hair in a sink drain, if the drainage angle gets clogged with pigment, even in a wide open angle, the aqueous humor could have a harder time draining, leading to increased IOP and damage to the optic nerve. This kind of glaucoma is a particular subset called Pigmentary Dispersion Syndrome

The end result will look something like this.

Please take the following Checkpoint Quiz